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. 2018 Dec 12;9:2939. doi: 10.3389/fimmu.2018.02939

Figure 2.

Figure 2

Mechanisms of immune tolerance to food allergens. Induction of food tolerance takes place in the gut when the immune cells encounter food antigens. Several cell types are involved in the antigen uptake: goblet cells, microfold (M) cells, intestinal epithelial cells, CX3CR1+ macrophages (MØ), and CX3CR1+dendritic cells. CX3CR1+ DCs and CX3CR1+ MØ, are capable of extending dendrites to capture antigens on the apical layer of epithelium in the gut lumen. Antigens taken up by CX3CR1+ MØ and goblet cells are transferred to CD103+CX3CR1− DCs, which subsequently migrate to draining lymph node in a CCR7 dependent manner. Production of retinoic acid and TGF-β foster differentiation of naïve T cells into regulatory T cells (Tregs). Retinoid acid-dependent induction of integrin α4β7 expression on Tregs is responsible for T cell homing to lamina propria. Tregs (Foxp3+), and Th3 cells inhibit Th2-dependent allergic inflammation and mast cell degranulation, through the production of IL-10 and TGF-β. Suppression of Th2-responses also engages regulatory B cells (Bregs) that contribute to food tolerance by producing IgG4.